This research paper studies the evolution of the Arab-Norman style in sacred monuments across Sicily, mainly in Palermo and adjacent cities, from the 9th to 12th century. The focus is on three edifices: the Monreale Cathedral, San Cataldo Church and Cathedral-Basilica of Cefalù. The premise of the research is to explore the cultural convergence of Byzantine, Moorish and Norman styles, and how it led to the creation of the unique, Arab-Norman style. Through a diverse, interdisciplinary line of action, using historical records, cultural context and previously written academic papers the extent of the influence of the three styles will be explored.